1. Field of the Invention
The present invention relates to a tool mounting and demounting device of a drilling machine.
2. Description of the Prior Art
A conventional tool mounting and demounting device for a drilling machine is explained with reference to FIG. 1. An inner cylindrical part f is connected to the lower end of the rotational main shaft a of a drilling machine. Shank e of the tool holder A grasps a tool, e.g. shank part c of a tap b, by the collet part d. The cylindrical wall g of the cylindrical part f is formed with through hole i in which balls h can move in the radial direction, the diameter of the balls h being larger than the thickness of the cylindrical wall g. A collar body j is mounted on the outer circumference of the cylinder wall g in such a manner that it can slide up and down along the cylindrical wall g. A large diameter part k is connected to the lower part of the inner wall of the collar body j. A recess 1 is formed in the tool holder A to which the balls h can be inserted. A safety guard m is mounted to the outer circumference of the tool holder A in such a way that it can freely be rotated relative to the tool holder.
In the case where the tap b is to be removed from the rotating main shaft a, and to be replaced with another rotary tool e.g. a drill, the tool holder A is still rotating when the safety guard m is gripped by one hand. Then, the collar body j is grasped by other hand and is lifted, and the large diameter part k of the lower part of the inner wall of the collar body j is shifted to the position of balls h. The balls h can then move radially out of the through hole i, and a part of each of the balls is inserted into the large diameter portion k. The engagement of the tool holder A and inner cylinder f by way of the balls h is thus released, and the tool holder A can be pulled out in a downwards direction.
After the tap and drill are exchanged for others, and the safety guard m is gripped, the tool holder A is inserted into the inner cylinder f and the collar body j is pulled downwards. The balls which have been shifted radially outward of the cylinder f are pushed radially inward to reengage the recess 1 of the tool holder A. As a result, the cylinder f and tool holder A are engaged through the balls h, and the drill may be driven by the rotary spindle a.
Such a tool mounting and demounting device of a drilling machine allows one to change a rotary tool (with the rotary tool holder as one body) while the rotational main shaft a is rotating, and is convenient for efficient exchange of a tool. However, for the purpose of increasing machining efficiency by positioning various rotary tools at a certain location, moving the rotary main spindle itself to that location and automatically exchanging a rotary tool, the driving mechanism employing balls as above cannot be used for the automatic control system because the tool holder A cannot be picked up. The above system also has the disadvantage of being complicated because of the use of balls, and requires complex machining technology resulting in high prices.